Constant flow gas analyzer



Sept. 14,' 1948. v GUlLLEMm; 1R n 2,449,067

CONSTANT FLOW GAS ANALYZER Filed July 29, 1946 #Trae/vs V Patented Sept. 14, 1948 UNITED STATES PATENT OFFICE coNs'rANr FLow cas'aNnLYzaa Victor Guillemln, Jr., Dayton, Ohio Anuman ruines. 194e. semi No. 686,834

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The invention described herein may be manul factured and used by or for the Government for governmental purposes without payment to me of any royalty thereon.

This invention relates.y to a continuous-flow type fluid analyzing apparatus and more par-` ticularly to one in which a iluid passing therethrough is divided into two portions one of which is subjected to a physical or chemical alteration that eiects its flow resistance. The resulting change in fluid pressure is indicated or recorded by a suitable gauge whose deflections are a quantitative measure of the properties of the fluid involved in the alteration.

In an alternative method of operation. the

change in flow resistance produced by the physical or chemical alteration is compensated by a manually operated resistanceraltering means, the gauge then functioning as anu1l" meter to indicate when compensation has been attained. 'I'he compensating means is calibrated and its 'movement is the quantitative measure of the fluid property being determined.

` For example, in the case of a fluid consisting of a mixture of gases, the alteration' could be the absorption of one oi the components. and

nects the juncture of two flow tubes in one iiow passage and the other side of the differential pressure responsive indicating means connects the juncture of two flow tubes in the other ow passage, analogous to the arrangement of the galvanometer in the Wheatstone bridge circuit, that is indicative of any change in flow resist'- ance in a flow tube corresponding to the arm containing the unknown electrical resistance of the Wheatstone bridge circuit fromwhich certain iluid characteristics may -be determined. One important feature of the present` invention is that pressure variations 'resulting from the changes in question are'indicated on a single gauge. It may therefore be made direct reading, requiring no computations to attain the desired values. Another important feature is that the gauge'is affected only by the pressuredifierences produced by the physical or chemical changes amended April 30', 1928: 370 0. G. 757) and not by the total pressure driving the fluid 4 through the apparatus. This makes lt possible to achieve very high sensitivity. For example, with a pressure of pounds per square inch applied across the apparatus, the indicating gauge can be chosen to measure pressures as low as Moo pounds per square inch. Thus changes of the o rder of one part in 10,000 can be measured. Many devices are known in which a change in the properties of a fluid is recorded as a change in the flow resistance. These are, however, all oi the ,type in which the flow resistance before and after the change is measured respectively by one of two separate gauges. These devices are therefore more complicated than the present invention. They are not inherently direct reading, and. what is more important, the gauges read thetotal pressures acting on the fluidy and it is therefore not possible to achieve the high degree o1 sensitivity required for precise analysis without resorting to complicated and costly pressure indicating devices.

The primary object of this invention is the provision of a continuous-flow typeiiuid analyzing apparatus from which certain characteristics of a fluid flowing therethrough may be determined.

Another object of this invention is to provide a continuous-flow type iiuid analyzing apparatus wherein certain fluid characteristics may be deduced from the indications of a pressure differential indicating means connected between two fluid flow paths of a divided uid conduit in which at least one `fluid ow path includes a fluid altering means. i

A further object of this invention is to provide an apparatus for quickly and accurately analyzing iluids' by the use of a single pressure differential indicating means connecting two flow passages in a divided portion of a fluid conduit intermediate flow control means upstream and a fluid altering means downstream being located i'n one ow passage, and a flow control means "upstream and a volume compensating means with inlet and outlet flow control means downstream being located in the other flow passage wherein certain characteristics ofthe fluid passing through the conduit may be determined.

A still further object of this invention is fthe provision of a continuous-flow type fluid analyzing apparatus in which the determination of certain characteristics of fluid flowing therethrough may be quickly and accurately determined by the use of single pressure diiferential indicating means connecting a junction of two ow tubes analyzed.

junction with the accompanying drawing wherein simple embodiments are shown diagrammatically to illustrate the invention, in which:

Fig. 1 is a diagrammatical representation of the apparatus exemplifying the subject invention;

Fig. 2 is a diagrammatical representation oi another embodiment of the invention;

Fig. 3 is a partial diagrammatlcal representa- 25. A piston 32 is adjustably reciprocable in the cylinder 21 by an adjusting screw 33 threadedly cooperative in an upper end Wall 34 of the cylinder 21. By regulating the height of the piston 32 in cylinder 21 the volumeof the compensating cell 26 can be regulated to balance the volume of the absorption cell 24. The ilow resistance through the compensating cell 28 may be varied by the needle valves 29 and 3| to match the resistance of the absorption cell.

Where it is desirable to use matched absorption and volume cellsy a detachable dummy volume tion of a removable volume compensating cell for a flow passage of the apparatus; and

Fig. 4 is a partialdiagrammatlcal representation of a graduated ilow resistance compensating device for a ilow passage of the apparatus.

Describing the invention more in detail, with reference particularly to Fig. l,there is shown diagrammatically a fluid conduit I0 having a i fluid inlet portion II Vand a uid outlet portion I2 separated by a fluid conducting divided portion forming two flow passages of ilrst and sec# ond flow tubes I3 and I4, I5 and I6, respectively. The rst ow tubes I3 and I5 of each iiow passage have adjustable needle valves I1 and I8,

respectively, therein for controlling the resistance to fluid ilow through the respective flow tubes I3 and I5. Pressure transmitting conduits I3 and 20 connect the two ow passages at the junction of the first and second ow tubes I3 and I4, and I5 and I6, respectively, at 2| and 22.

A differential pressure responsive indicator 23 is in operative communication withthe pressure transmitting conduits I9 and 20. This indicator may be a dlierential pressure gauge, manometer, a recording pressure device, or any other desirable pressure responsive indicating means but is illustrated herein for simplicity as merely a differential pressure gauge.

In one flow passage I5-I6 there is an absorption cell 24, or any suitable reaction cell, arranged at the entrance to the second flow tube I5, as shown, adapted to be detachable as by rubber coupling 25 arranged to slip over the ends of the flow tube I5 and the conduit for the absorption cell 24 in the well known manner. The absorption cell i 24 may be lled with suitable chemicals for absorbing certain fluids of a fluid mixture to be In practice, because of difference in volume in the two ilow passages I3-I4 and I5-I 6 caused by the absorption cell 24, there will be transient unbalanced pressures whenever there is a change of now. In order to maintain equal volumes in the two ow passages I3--I4 and I5-I6, to avoid unnecessary surges upon admitting or shutting ol! fluid to the apparatus, there is included in the other ilow passage I3-I4 an adjustable compensating volume cell, generally designated by the reference character 26, arranged at the entrance to the flow tube I4, as shown. The compensating volume cell 26 comprises a member with a cylindrical bore 21 having an inlet conduit 28, with an adjustable needle valve 29 therein, and an outlet conduit 30, with an adjustable needle valve 3| therein, connected to the flow tube I4 such that duid tlowing into the flow tube I4 must pass through the adjustable compensating volume cell lcell 35 may be arranged in place of the compensating cell 23, as illustrated in Fig. 3, and attached in the same manner as the absorption cell 24 is attached to the flow tube I3. The compensating volume cells 28 or 35 have no effect on fluid flowing therethrough except to compensate for the absorption cell 24 with regard to volume and ow resistance.

The embodiment shown in Fig. 2 is similar in many respects to the embodiment of Fig. 1 in which like reference characters designate like parts and portions. It may be noted in this figure that the flow tube I4 does not necessarily require a volume compensating cell. The ilow tube I5, in this form of the invention, is surrounded by an electrical heater element 35 for conducting heat to the ow tube I6 from the heater coil 31.

In Fig. 4, 38 is a graduated needle valve or any other suitable graduated device for altering the flow resistance through flow tube I4. The extent of this alteration may be read on a suitable scale. as shown at 39.

In the actual embodiment of the invention the flow tubes I3, I4, I5, and I6 will normally be fine capillary tubes of, for example, .1 to 1 millimeter bore size that have relatively high resistance to fluid ow, while the parts I I, I2, I3, 20, 24, 23 and 35 have a relatively negligible resistance. Also, thgrcsi'stances of the four flow tubes I3, I4, I5,

'd I6 are preferably made ne'arly alike although the flow through the flow passage I3--I4 may be somewhat diierent than the ow through the iiow passage I5-I6 without causing detrimental results if the resistance to the iiow in the flow value and to maintain this flow, or the total pressure differential between inlet I I and outlet I2,

constant, either automatically or by manual adjustment.

In operation of Fig. 1 let it be assumed, by Way oi example, that a mixtureof a gas A and gas B is to be analyzed for gas A content. The cell 24 lis charged with a substance which absorbs one of the gases, say A, but not B. By any suitable means, pure gas B is passed through the apparatus, and the flow is adjusted until the pressure differential between inlet II and outlet I2 has the desired value. This pressure differential is maintained constant throughout all subsequent operations. The resistances of the flow tubes I3 and I5 are adjusted by the needle valves I1 and Il until they are in the same proportion as the resistances of ilow tubes I4 and I3, including the absorption cell 24 and compensating cell 25 or 35. This balanced" condition will be indicated by I) pressure diilerence across the gauge 23. If now the unknown mixture of gases A and B is introduced into the iluid conduit I0 at II, the gas A will be 5 v absorbed in the absorption cell 2l and the flow of gas through the flow tube II will be less than the tlow through'the flow-tube I5. The flow through flow tubes I3 and I4 will, however, remain unchanged. Therefore, the pressure at the junction 22 of flow tubes I3 and Il will not be altered, but the pressure at the junction 2I of flow tubes I5 and I6 will be lowered by anfamount depending on the proportion of gas A in the mixture. The pressurein the flow passage I3I4 at the junction 22 is transmitted to one side of the pressure differential gauge 23 by the pressure transmitting conduit I9 and the pressure now existing in the ow passage IS-IG at the junction 2l is transmitted to the other-side of the pressure differential gauge 23 by the pressure transmitting conduit 20 to cause registration on the pressure differential gauge which difference in pressure between the junction points 2| and 22 will give a negative reading denoting a lowerpressure at the junction 2I than at the junction 22. By proper calibration of the gauge 23, with known mixtures of gases A and B, a scale maybe constructed for this gauge to indicate directly the proportion of gas A in 'any given unknown mixture.

The apparatus of Fig. 2 may be used to measure the change of viscosity of a fluid due to very slight changes of temperature. With the heater 38 inoperative, a suitable flow of fluid is established through the apparatus, and the initial balanced condition is obtained as in the operation of Fig. 1. When the heating element is made operative, the viscosity of the fluid, while flowing through the flow tube IB, will `be-altered, and the pressure at the junction 2l of ow tubes l5 and I-'i will be changed. lThe deflections of the gauge 23 will be a measure of this change. The temperature diierence between the fluid in flow -tubes I3, Il, i5, and IB may be determined by thermocouples or any other suitable means. With constant predetermined temperatures in the iiow tubes I3, I4, I5, and I6, the gauge 23 may be designed to read temperature coefficient of viscosity directly.

The present invention may also'be operated as a null instrument instead of a direct indicating instrument by addition of the parts shown in Fig. 4. In this method of operation, the gauge mi is balanced under all conditions of operation? This is accomplished by actuating the graduated needle valve 38 thereby altering the flow resistance through ow tube I4 by a known amount sufficient to compensate for the change of ow audios? fluid.

It is understood that the parts shown 1n Figures l, 2, 3, and 4 may be rearranged and combined in various ways without departing from the scope ofthis invention. For example, one type of fluid altering means might be arranged at the entrance of flow tube Il and another fluid altering means be arranged simultaneously at the entrance of flow tube I-B.

The apparatusof this invention may be used to give continuous indication and record of such varied quantities as the per cent impurities of the output of commercial gas manufacturing plant or the temperature coeflcient of viscosity of 'lubricating oil. It could. of course, be made to give analarm when the indicated quantities exceeds a predetermined maximum. More generally, `the apparatus is capable of indicating, measuring. and recording any physical or chemical change of a uid which aiects flow resistance.

The present invention is not limited to the diagrammatical details set forth as illustrated resistance through flow tube I6 caused by such devices as or 36, compensation being complete when the gauge 23 indicates 0. The known extent to which the iiow resistance through flow tube iii must be altered to bring the gauge 23 back to zero or null position, after it has been deflected, is read on the graduated scale '39 and is then a measure of the fluid alteration that is being investigated. This method of operation, while less convenient than the direct reading method, has the advantage that the null` adjustment is independent of the rate of ow of uid through the apparatus.

In the interest of obtaining the greatest possible accuracy the duid analyzer apparatus may be placed in a chamber, or in a Water tank, such that air currents varying in :mperature will not affect the viscous characteristics of the sample being tested where not intended. Further, larger error due to slight temperature changes of the 4 change of flow resistance in said s econd flow tube of said one flowpassage, a manually adjustable volume compensating means in the other flow passage for equalizing the volume in the said second flow tube of said other flow passage with the volume in the said second flow tubeof the said one ow passage including the said first mentioned means to prevent sudden surges of Iluid flowing through said fluid conduit from altering the proportional ilow in said two flow passages, and a pressure responsive indicating means connecting the two said iiow passages at the junction respectively vof the said first and second flow tubes for indicating the pressure differential between said ow passages resulting from a change of flow resistance upon operation of said first mentioned means.

2. A fluid analyzing apparatus comprising, a fluid conduit divided into two flow passages in a portion thereof, each of said flow passages being divided into first and second flow tubes through which fluid is adapted to flow successively, flow control valves in the first flow tube of each of said flow passages for individually controlling the uid flow through each said flow passage, means at the entrance of the second flowl tube of one of' said ow passages operative for producing a change of fiow resistance through said last mentioned second flow tube, an adjustable manually controllable volume compensating cell and a flow resistance compensating means associated with the second flow tube of the other of said flow passages for maintaining equal volume in said two ow passages to prevent any proportional change in flow resistance upon a change in flow and for compensating the change of flow resistance produced in the second tube of the said one flow passage by said first mentioned means,

respectively, said flow resistance compensating means having an indicator thereon forY registering the degree of compensation for resistance anda pressure responsive indicating means connecting the two said ow passages at the junction respectively of the said iirst and second ow tubes for indicating the pressure differential between the two said flow passages.

3. A uid analyzing apparatus comprising a uid conduit divided into two flow passages in a portion thereof, said conduit having means operatively associated with one of said ow passages ior producing a change of ow resistance in said one ow passage, an adjustable volume compensating means in the other fiow passage for maintaining equal volume in said two ow passages wherein sudden. surges of fiuid passing through said fluid conduit are ineiective to change the proportional flow through saidtwo flow passages. and a pressure responsive indicating means connected across the two said flow passages for indicating the pressure -diierential between said two ow passages resulting from a 8 change o! ow resistance upon operation of said rst mentioned means.

VICTOR GUELEMIN, JR.

REFERENCES CITEDl The following references are of record in the ie of this patent:

UNITED STATES PATENTS Number Name Date 854,696 Jones May 21, 1907 1,112,432 Brach Oct. 6, 19`4 2,139,902 Malmgren Dec.' 13, 1938 2,263,335 Heinz Nov. 18, 1941 2,370,817 Shanley Mar. 6, 1945 FOREIGN PATENTS Number Country Date 329,386 Germany Nov. 23, 1920 375,899 Germany June 14, 1923 396,529 Germany June 5, 1924 486,287 Germany Oct. 31, 1929 570,451 France Jan. 16, 1924 

